Mahé and St. Joseph Atoll, Seychelles
October-November 2022
Expedition Goals and Summary
One of the most serious impacts humans face as a result of climate change is a predicted decrease in the dissolved oxygen (O2) content of the world’s oceans due to the warming of the ocean’s surface layer. Documenting the extent to which this process has occurred (and is occurring) is of utmost importance, given that O2 plays a direct role in the cycling of biogeochemically fundamental elements. Despite the consistent agreement amongst climate models regarding the expansion of ODZs in future warming scenarios, however, time series recording the expansion of oxygen minimum zones across the Anthropocene largely do not exist.
The location of the Seychelles makes it ideally suited to develop a time series of δ15N in scleractinian corals as a proxy for the expansion of water column denitrification (and by extension ODZs). Led by myself, Ph.D. student Tanja Wald, and guest researcher Holger Anlauf, and in collaboration with the Save Our Seas Foundation and the University of the Seychelles, we collected coral cores, coral tissue, and seawater samples to better characterize the extent of ODZ expansion in the Indian Ocean (at St. Joseph’s Atoll) and to better gauge anthropogenic impacts on nutrient cycling (on the reefs of Mahé). Together the data generated by this project will help provide information about direct and indirect human impacts on the reefs of the Southwestern Indian Ocean.